Our own LZO (1X) implementation, under LGPL and optimized for readability.

Tested on CamStudio sample files.

Originally committed as revision 4840 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 167 insertions, 0 deletions

diff --git a/libavcodec/lzo.c b/libavcodec/lzo.c
new file mode 100644
index 0000000000..a123abb497
--- /dev/null
+++ b/libavcodec/lzo.c
@@ -0,0 +1,167 @@
+/*
+ * LZO 1x decompression
+ * Copyright (c) 2006 Reimar Doeffinger
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+#include "common.h"
+#include "lzo.h"
+
+typedef struct LZOContext {
+    uint8_t *in, *in_end;
+    uint8_t *out, *out_end;
+    int out_size;
+    int error;
+} LZOContext;
+
+/**
+ * \brief read one byte from input buffer, avoiding overrun
+ * \return byte read
+ */
+static inline int get_byte(LZOContext *c) {
+    if (c->in < c->in_end)
+        return *c->in++;
+    c->error |= LZO_INPUT_DEPLETED;
+    return -1;
+}
+
+/**
+ * \brief decode a length value in the coding used by lzo
+ * \param x previous byte value
+ * \param mask bits used from x
+ * \return decoded length value
+ */
+static inline int get_len(LZOContext *c, int x, int mask) {
+    int cnt = x & mask;
+    if (!cnt) {
+        while (!(x = get_byte(c))) cnt += 255;
+        cnt += mask + x;
+    }
+    return cnt;
+}
+
+/**
+ * \brief copy bytes from input to output buffer with checking
+ * \param cnt number of bytes to copy, must be > 0
+ */
+static inline void copy(LZOContext *c, int cnt) {
+    if (c->in + cnt > c->in_end) {
+        cnt = c->in_end - c->in;
+        c->error |= LZO_INPUT_DEPLETED;
+    }
+    if (c->out + cnt > c->out_end) {
+        cnt = c->out_end - c->out;
+        c->error |= LZO_OUTPUT_FULL;
+    }
+    do {
+        *c->out++ = *c->in++;
+    } while (--cnt);
+}
+
+/**
+ * \brief copy previously decoded bytes to current position
+ * \param back how many bytes back we start
+ * \param cnt number of bytes to copy, must be > 0
+ *
+ * cnt > back is valid, this will copy the bytes we just copied.
+ */
+static inline void copy_backptr(LZOContext *c, int back, int cnt) {
+    if (c->out - back < c->out_end - c->out_size) {
+        c->error |= LZO_INVALID_BACKPTR;
+        return;
+    }
+    if (c->out + cnt > c->out_end) {
+        cnt = c->out_end - c->out;
+        c->error |= LZO_OUTPUT_FULL;
+    }
+    do {
+        *c->out++ = c->out[-back];
+    } while (--cnt);
+}
+
+/**
+ * \brief decode LZO 1x compressed data
+ * \param out output buffer
+ * \param outlen size of output buffer, number of bytes left are returned here
+ * \param in input buffer
+ * \param inlen size of input buffer, number of bytes left are returned here
+ * \return 0 on success, otherwise error flags, see lzo.h
+ */
+int lzo1x_decode(void *out, int *outlen, void *in, int *inlen) {
+    enum {COPY, BACKPTR} state = COPY;
+    int x;
+    LZOContext c;
+    c.in = in;
+    c.in_end = in + *inlen;
+    c.out = out;
+    c.out_end = out + * outlen;
+    c.out_size = *outlen;
+    c.error = 0;
+    x = get_byte(&c);
+    if (x > 17) {
+        copy(&c, x - 17);
+        x = get_byte(&c);
+        if (x < 16) c.error |= LZO_ERROR;
+    }
+    while (!c.error) {
+        int cnt, back;
+        if (x >> 4) {
+            state = BACKPTR;
+            if (x >> 6) {
+                cnt = (x >> 5) - 1;
+                back = (get_byte(&c) << 3) + ((x >> 2) & 7) + 1;
+            } else if (x >> 5) {
+                cnt = get_len(&c, x, 31);
+                x = get_byte(&c);
+                back = (get_byte(&c) << 6) + (x >> 2) + 1;
+            } else {
+                cnt = get_len(&c, x, 7);
+                back = (1 << 14) + ((x & 8) << 11);
+                x = get_byte(&c);
+                back += (get_byte(&c) << 6) + (x >> 2);
+                if (back == (1 << 14)) {
+                    if (cnt != 1)
+                        c.error |= LZO_ERROR;
+                    break;
+                }
+            }
+        } else
+        switch (state) {
+            case COPY:
+                cnt = get_len(&c, x, 15);
+                copy(&c, cnt + 3);
+                x = get_byte(&c);
+                if (x >> 4)
+                    continue;
+                cnt = 1;
+                back = (1 << 11) + (get_byte(&c) << 2) + (x >> 2) + 1;
+                break;
+            case BACKPTR:
+                cnt = 0;
+                back = (get_byte(&c) << 2) + (x >> 2) + 1;
+                break;
+        }
+        copy_backptr(&c, back, cnt + 2);
+        cnt = x & 3;
+        if (cnt)
+            copy(&c, cnt);
+        else
+            state = (state == COPY) ? BACKPTR : COPY;
+        x = get_byte(&c);
+    }
+    *inlen = c.in_end - c.in;
+    *outlen = c.out_end - c.out;
+    return c.error;
+}